1. Technical Field
The present invention relates to redundant sensing switches. In particular, it relates to an improved RF redundant sensing switch which dynamically switches signal sources based on relative differences between those two sources.
2. Background
RF redundant sensing switches are used in a variety of applications to offer back up redundancy of the same signal in the event of a failure of the primary signal, therefore increasing the reliability of the system. To illustrate how RF redundant sensing switches are used, an example will be discussed which illustrates how these switches are used by cable television systems.
In cable television systems, RF redundant sensing switches are often used in the headends and hubs of cable systems. The RF redundant sensing switches offer redundant paths which can be switched based on signal quality. They can be used in conjunction with any active RF device and/or RF path, such as a redundant optical and/or RF ring architecture by switching between the primary and secondary signal sources on the A/B signal paths.
Conventional systems monitor the level of primary signal source. If an error is detected, the RF redundant sensing switch will switch from the primary signal source to the secondary signal source. Typically, an error is detected when the primary signal disappears completely or drops below a predetermined threshold level.
Alternatively, other conventional systems monitor the secondary signal in addition to the primary and switch from the primary to the secondary signal path only when the secondary signal is above a predetermined threshold level. The threshold levels in the prior art systems do not necessarily have to be the same.